Carbonate-hydroxide chemical-garden tubes in the soda ocean of Enceladus: Abiotic membranes and microtubular forms of calcium carbonate

We present the results of laboratory experiments with carbonate-hydroxide chemical gardens designed to reproduce the possible conditions of mineral precipitation at a hydrothermal vent in the alkaline ocean of Saturn's moon Enceladus. We describe the membranaceous and tubular structures that form in this self-organized system. We analyse the resulting material morphology, composition and microstructure using scanning electron microscopy (SEM), micro-Raman spectroscopy, X-ray diffraction (XRD), and energy dispersive X-ray analysis (EDX). We find that, as well as more common minerals such as calcite and vaterite, a significant amount of gaylussite may form under conditions present in Enceladus' soda ocean. We discuss how gravity differences may affect the growth of such chemical-garden structures on Enceladus compared to on Earth.